Epilepsy is a major cause of disability worldwide. Many people with epilepsy are treatment resistant, and are also at risk for a condition called sudden death. Interventions that reduce both seizures and sudden death have yet to be developed. Human data indicate that omega-3 fatty acids, (EPA and DHA, the principal ingredients of fish oil), reduce cardiac arrhythmias and sudden death in those with heart disease. EPA and DHA also reduce seizures in accepted animal models of epilepsy. If omega-3 fatty acid (fish oil) supplementation reduces seizures and the risk for sudden death, it would represent a major advance in the treatment of epilepsy. The central goals of this study are to determine if fish oil reduces seizures, and reduces the risk of cardiac arrhythmias and sudden death in people with epilepsy. A secondary goal is to determine if fish oil improves cognition in this population. We propose a pilot clinical trial, which explores the following Specific Aims: First, to obtain preliminary data regarding the safety and effectiveness of fish oil compared with placebo in reducing seizure frequency and seizure severity. Second, we will evaluate the effect of fish oil on variables related to the risk of sudden death, especially heart rate variability. This study is designed to be a proof of concept study of fish oil in epilepsy. Thirty children and adults, ages 16 - 70, with three or more simple partial, complex partial, or secondarily generalized tonic-clonic seizures per month will be enrolled in a 36-week study. If successful, this study will lay a foundation for future studies of fish oil for epilepsy. Public Health Relevance: Epilepsy is a major cause of injury and disability throughout the world. Many people with epilepsy are poorly controlled, and are at risk for a condition called sudden death in epilepsy. The purpose of this study is to investigate whether omega-3 fatty acids (as fish oil) benefit people with epilepsy by reducing seizures, preventing sudden death, and improving memory and thinking processes.